SH3BP5L

SH3BP5L is a guanine nucleotide exchange factor (GEF) for the small GTPase RAB11A that controls endosomal recycling and the routing of cargo to the plasma membrane (PMID:34128958, PMID:39051763). Recruited to early endosomes (in part by RAB22A), SH3BP5L activates RAB11A to redirect cargo such as EGFR from early endosomes into recycling endosomes destined for microvesicle shedding (PMID:39051763), and it nucleates assembly of a RAB11A–KIF5B anterograde motor complex that drives β1 integrin recycling and α3β1 surface exposure (PMID:41623179). Through these activities SH3BP5L-dependent RAB11A activation supports epithelial cyst lumen formation (PMID:34128958), microvesicle biogenesis (PMID:39051763), and integrin-driven cell spreading and metastasis, such that loss of SH3BP5L or its GEF catalytic activity reduces metastatic dissemination in vivo (PMID:41623179). Its GEF activity is held in check by Tankyrase-mediated suppression, which is itself relieved by the E3 ubiquitin ligase RNF146 acting to reduce Tankyrase abundance (PMID:34128958).

1. 2021 High

   Established SH3BP5L as a RAB11A GEF and embedded it in a regulatory circuit, answering both what activates RAB11A in lumen formation and how that activation is controlled.

   Evidence BioID interaction proteomics with loss-of-function epithelial cyst lumen assays and genetic epistasis (RNF146 → Tankyrase → SH3BP5L → RAB11A)

   PMID:34128958

   Open questions at the time

   • No structural basis for nucleotide exchange on RAB11A defined
   • Direct biochemical demonstration of RNF146/Tankyrase modification of SH3BP5L not detailed in the readout
   • Cargo recycled during lumen formation not specified
2. 2024 Medium

   Defined how SH3BP5L is recruited to act, showing RAB22A brings it to early endosomes to activate RAB11A and reroute EGFR into microvesicles, linking the GEF to cargo sorting and extracellular vesicle biogenesis.

   Evidence RAB GTPase family screening, co-immunoprecipitation/interaction assays, and functional microvesicle formation assays

   PMID:39051763

   Open questions at the time

   • Single-lab interaction data without reciprocal in vivo validation
   • Whether RAB22A recruitment generalizes beyond EGFR cargo unknown
   • Mechanism coupling RAB11A activation to microvesicle shedding not resolved
3. 2026 High

   Connected SH3BP5L GEF activity to a defined effector output and disease phenotype, showing it assembles a RAB11A–KIF5B motor complex driving integrin recycling and metastasis.

   Evidence FRET RAB11A activation sensors, GEF-dead mutagenesis, integrin recycling assays, and zebrafish/mouse metastasis models

   PMID:41623179

   Open questions at the time

   • Structural detail of the RAB11A–KIF5B complex assembly not resolved
   • Whether Tankyrase/RNF146 regulation operates in the metastatic context untested
   • Selectivity of GEF inhibition for therapeutic use not established

• How SH3BP5L catalytic and recruitment activities are integrated across distinct cellular contexts (lumen formation, microvesicle biogenesis, metastasis) and structurally executed remains open.
• No structural model of SH3BP5L or its RAB11A complex
• Full cargo repertoire beyond EGFR and integrins unknown
• Interplay between RAB22A recruitment and Tankyrase/RNF146 regulation uncharacterized